The present invention relates to a pharmaceutical or cosmetic carrier or composition for topical application onto skin and/or mucosal membranes (e.g., the mucosa of the nose, mouth, eye, ear, vagina or rectum). More particularly, the present invention relates to (i) a cosmetic or pharmaceutical carrier or composition characterized by rheological properties which render the carrier or composition semi-solid at rest and liquid upon application of shear forces (e.g., spread forces) thereto; (ii) methods of preparing same; and (iii) methods of utilizing same for treating a variety of skin or mucosal membrane diseases or disorders.
Most of the skin or mucosal membrane diseases or disorders are the result of inflammation caused by inflammatory agents, such as, but not limited to, bacterial, fungal, viral, parasitic, autoimmune, allergic, hormonal and/or malignant inflammatory agents. The most common skin diseases or disorders include eczema, psoriasis and dermatitis, including contact dermatitis, atopic dermatitis and seborrheic dermatitis.
Eczema and dermatitis result from inflammatory processes that involve the upper dermis and epidermis of the skin. When eczema develops, the keratinocytes in the epidermis distend from one another and fluid is accumulated there amongst in a process known as spongiosis.
In chronic forms of eczema or dermatitis the main change include thickening of the epidermis, which leads to itching, roughening and scaling of the skin surface. The loss of water from the skin leads to inflammation of the horny layer, which later result in cracked and sore skin.
Dermatitis is further classified into contact dermatitis (allergic or non allergic), atopic dermatitis and seborrheic dermatitis.
Non allergic contact dermatitis occurs in response to skin irritants, such as acids, alkalis, oils, detergents and solvents.
Allergic contact dermatitis occurs as a result of sensitization to repeated exposure to an antigen. Allergic contact dermatitis appears in skin areas that were in direct contact with the antigen.
Atopic dermatitis, which affects mainly infants, is characterized by sensitization of the skin to a wide range of common antigens.
Seborrheic dermatitis affects the scalp and other hairy areas, the face, and flexural areas and results from yeast or bacteria induced inflammation. Most people suffer from dandruff which is a mild form of seborrheic dermatitis.
Psoriasis is a dominant autosomal inherited inflammatory disease characterized by enhanced proliferation of keratinocytes which proliferation leads to formation of scaly plaques on, for example, the knees, elbows, buttocks, and which are esthetically unpleasant and cause discomfort to the affected subject.
Skin diseases or disorders are usually treated by creams, gels or ointments containing antifungal agents, steroidal agents and/or antibacterial agents. In many instances such creams, gels and ointments are difficult to spread, result in a greasy and sticky appearance and are usually not appealing for use.
Genital infections are caused by fungal, viral and microbial agents. Genital infections are treated either systematically, or by the use of creams, ointments or pessaries, which usually leak or otherwise fail to spread well and lead to ineffective therapeutic concentration of the therapeutically active agent(s) therein.
Genital herpes infections are widespread from the 70's and apart from the discomfort they inflict, genital herpes infections may, in some cases, develop into severe disease. Presently, there is no effective medication for genital herpes.
Trichomoniasis is an infection of the urogenital tract caused due to infection by the protozoan Trichomonas vaginalis. Trichomoniasis is associated with uncomfort itching and vaginal excretion in women.
Candidiasis is caused by Candida albicans and results in itching in the genital area and white discharge therefrom.
Mucosal membrane inflammations can affect other organs such as for example, the eye. Conjuctivitis, caused by different types of bacteria, such as, but not limited to, Staphylococcus aureus, Streptococcus pneumoniae or Haemophilus influenzae, is generally treated with antibiotic ointments, e.g., bacitracin 500 U/g or gentamicin 0.3 percent ophthalmic ointment instilled into the affected eye. The compliance to these ointments is usually poor due to the sticky feeling they exert.
As is evident from the above descriptions, one of the important routes of administration of a drug for treating a skin or mucosal membrane is by topical application of a drug onto the skin or mucosal membrane. This method is useful for local treatment but it is also possible to apply pessaries via the rectum as an efficient delivery method of systemic agents that are not degraded in the intestine.
Many pharmaceutical carriers are presently known, most of them have disadvantages when topically applied onto the skin or mucosal membranes. For example, when ointments containing petroleum as a carrier are applied onto a skin wound, metabolic products and excreta from the wound cannot be easily removed therefrom because of the difficulty of passing through the hydrophobic petroleum barrier. In addition, the active drug ingredient, which is dissolved or dispersed in the petroleum carrier, is not efficiently absorbed into the wound tissue, thus, the efficacy of the drug is affected. Another example is ophthalmologic ointments, which are applied into the eye, and make the eye area sticky and uncomfortable. Moreover, in physiological aspect, petroleum restricts respiration of a wound tissue and is disturbing to the normal respiration of the skin.
Many groups of drugs including, for example, antibiotic, antifungal, antiinflammatory, anesthetic, analgesic, antiallergic, corticosteroid, retinoid and antiproliferative medications are preferably administered typically using a hydrophobic carrier such as petroleum. However, due to the undesirable consistency of petroleum and similar hydrophobic carriers, their topical use is limited. An additional disadvantage of petroleum-carrier including products relates to the greasy feeling following their topical application to the skin or mucosal membranes.
Besides petroleum, other hydrophobic pharmaceutical carriers are known, including liquid paraffin, lanolin, beeswax, vegetable oil, glycerin monostearate, higher alcohols, polyethylene glycol and some emulsifying agents. All of these agents either suffer the limitations described hereinabove with respect to petroleum or have undesirable (fast) flow properties.
Several hydrophobic liquids, e.g., mono-and poly-unsaturated oils from vegetable and marine sources, silicone oils, mineral oils, and liquid hydrophobic plant-derived oils are known for their therapeutic effects when applied topically. Oils may also contain essential nutritional constituents, such as oil-soluble vitamins (e.g., vitamin A and vitamin E), minerals and other therapeutically effective constituents. Administration of such therapeutic oils in a liquid form does not exert sufficient amounts of the therapeutic agents, because of the oil flow-spread properties. Other examples of therapeutic oils include mineral and silicone oils, which are useful for the treatment of skin dehydration and other medical diseases or disorders. These oils are also liquid at ambient temperature.
There is thus a widely recognized need for, and it would be highly advantageous to have a new pharmaceutical or cosmetic composition or carrier which is semi-solid at rest and which liquefies upon application of shear forces thereto, because such a pharmaceutical or cosmetic composition or carrier can be topically applied as a semi-solid onto an affected area and then turn into a liquid upon spreading, resulting in faster absorption and less greasiness and stickiness.